Ethylene-alpha-olefin elastomer compositions



United States Patent 3,415,769 ETHYLENE-a-OLEFIN ELASTOMER COMPOSITIONS David M. Todd, Warrington, and William D. McDavid, Pensacola, Fla., assignors to Tenneco Chemicals, Inc., a

corporation of Delaware No Drawing. Filed May 24, 1965, Ser. No. 458,460 Claims. (Cl. 260-293) ABSTRACT OF THE DISCLOSURE Oligomers of cyclic monoterpene hydrocarbons, which have the formula (C H wherein n is an integer in the range of 2 to 4 and which have boiling points in the range of 170 C. to 240 C. at 10 mm. can be used to tackify and at the same time to soften and plasticize elastomeric ethylene-a-olefin polymers. These oligomers do not adversely affect the rate at which the elastomer compositions cure or the physical properties of the compositions; they are resistant to oxidation and are not readily extracted from the compositions by solvents or by alkalies.

This invention relates to ethylene-a-olefin elastomer compositions and to processes for their production. More particularly, it relates to compositions of this nature that contain oligomers of cyclic monoterpene hydrocarbons as the plasticizer-tackifier.

Rubbery, substantially amorphous ethylene-a-olefin polymers have become of increasing commercial interest with the introduction of low pressure processes for their manufacture. These polymers, however, like other synthetic rubbers, lack natural tack, and they require the addition of tackifiers as well as plasticizers before they can be used in elastomer compositions.

A number of materials have been suggested for use as plasticizers or tackifiers forethylene-a-olefin polymers, but none of them when used individually or in combination have imparted the desired combination of properties to the elastomer compositions. One combination of additives that has been widely used includes petroleum hydrocarbon oils as plasticizer and a liquid thermoplastic phenol-aldehyde resin as tackifier. The use of this combination of additives is not entirely satisfactory for many applications because the phenol-aldehyde resin interferes with the cure rate of both peroxide-cured ethylene-a-Olefin copolymers and sulfur-cured ethylene-wokfine-diene terpolymers and tends to have a deleterious effect on the physical properties of the elastomer compositions. In addition the phenol-aldehyde resins are r alkali-extractable and are susceptible to oxidation.

In accordance with the present invention, it has been found that oligomers of cyclic monoterpene hydrocarbons can be used to tackify and at the same time to soften and plasticize ethylene-a-olefin polymers. The use of the oligomers does not adversely affect the rate at which the elastomer compositions cure or the physical properties of the compositions. The oligomers are resistant to oxidation and are not readily extracted from the compositions by solvents or by alkalies.

The oligomers of cyclic monoterpene hydrocarbons that may be used in the; compositions of this invention are low molecular weight polymers of such cyclic monoterpene hydrocarbons as dipentene, limonene, ot-pinene, fi-pinene, p-cymene, carenes, camphene, and mixtures thereof. These oligomeres have the formula (C H wherein n represents an integer in the range of 2 to 8. Particularly advantageous results have been obtained with ethylene-propylene-diene terpolymers that contained as plasticizer-tackifier oligomers that were dimers or mixtures of dimers and trimers containing small amounts of tetramers and that were obtained by the polymerization of dipentene or turpentine. These preferred oligomers have boiling points in the range of 170 C. to 240 C. at 10 mm. pressure and molecular weights in the range of 270 to 450.

The terpene oligomers may be prepared by any suitable and convenient procedure. For example, they may be prepared by the thermal or catalytic polymerization of the appropriate terpene or mixtures of terpenes. In a preferred method for the preparation of the oligomers turpentine is polymerized in the presence of a Lewis acid catalyst and a hydrocarbon solvent. After distillation to remove the solvent, the polymer contains approximately 5% to 15% by weight of terpene monomers (principally upinene and fi-pinene), to by weight of terpene oligomers, and 5% to 40% by weight of higher polymers. While this material can be used without purification in the ethylene-a-olefin elastomer compositions of this invention, it is preferably distilled to separate the oligomers from the monomers and from at least a part of the higher polymers. Compositions having excellent combinations of physical properties have been obtained when the terpene oligomers used as plasticizer-tackifier contained as much as 15 percent of higher polymers.

Any of the elastomeric ethylene-wolefin polymers can be used in the practice of this invention. These include a Wide variety of normally-solid, rubbery ethylene-wolefin copolymers and ethylene-a-olefin-diene terpolymers. These polymers which are known in the art can be prepared by polymerizing ethylene with an oc-olefin or with an a-olefin and a diene by any of several methods. The preparation of these polymers is described, for example, in Belgian Patents No. 535,082, No. 538,782, No. 553,655, and No. 583,039 and in US. Patents No. 2,700,663, No. 2,726,231, No. 3,102,876, No. 3,153,023, and No. 3,154,528.

The OL-OlefiHS that can be polymerized with ethylene to form these copolymers and terpolymers are those that contain from 3 to 8, and preferably 3 to 6, carbon atoms per molecule with no branching closer to the double bond than the 4-position, for example, propylene, l-butene, 1- pentene, l-hexene, l-octene, 4-methyl-l-pentene, S-methyll-hexene, and the like. Both conjugated and non-conjugated linear and cyclic hydrocarbon dienes may be polymerized with ethylene and one or more of the aforementioned a-olefins to form the elastomeric terpolymers. These include 1,3-butadiene, isoprene, 1,3-pentadiene, 1,4- hexadiene, dicyclopentadiene, 5-rnethylene-Z-norbornene, 5-(2'-ethyl-2'-butenyl)-2-norbornene, Z-ethyl 2,5 norbornadiene, and the like.

The following are specific examples of the elastomeric polymers that may be used in the compositions of this invention: ethylene-propylene; ethylene-l-butene; ethylene-l-hexene; ethylene-propylene-1,3-butadiene; ethylenepropylene-isoprene; ethylene-propylene-dlicyclopentadiene; ethylene propylene-S-methyl-Z-norbornene; ethylene 1- butene-l,3-butadiene; ethylene-l-hexene-isoprene; ethylene-l-hexene-l,4-hexadiene; and the like. The preferred polymers are the ethylene-propylene-diene terpolymers which contain approximately 25 percent to 75 percent by weight of ethylene monomer units, 25 percent to 75 percent by weight of propylene monomer units, and 0.5 percent to 5 percent by weight of diene monomer units and which have iodine numbers below approximately 30.

The ethylene-a-olefin polymers may be used as such in the novel elastomer compositions, or they may be extended with approximately 50 percent to 200 percent, and preferably percent, based on the weight of the polymer, of a parafiinic, aromatic, or naphthenic oil prior to their use.

The amount of terpene oligomers that is incorporated in the ethylene-a-olefin elastomer compositions is that in the presence of aluminum chloride and distilling the product to obtain fractions of turpentine Elongation at Break Shore A2 Hardness 15 Min. 30 Min. 45 Min. 15 Min. 30 Min. 45 Min.

Example 3 at 40 dimers containing varying amounts of higher polymers (trimers-pentamers) The compounded stocks were press cured at 320 F. and 500 p.s.i., half for 15 minutes and half for 45 minutes. The plasticity, modulus of elasticity, elongation, and hardness of the compositions were determined by the procedures described in Example 1. Cure Index is the time in minutes required for the Mooney viscosity to rise 30 points above the scorch point. The properties of the compositions are given in Table III.

TABLE III Physical Data for Cured Stock at 10 Min. and 45 Min. Cure Times Modulus of Elasticity Tensile Strength 30 Min. 45 Min. 15 Min. 30 Min. 45 um.

One hundred parts of an ethylene-propylene-diene terpolymer extended with 100 percent of a naphthenic oil (Royalene X400) was compounded in a Banbury mill with 1 part of stearic aci 60 parts of High Abrasion Furnace Black, 5 parts of zinc oxide, 05 part of mercaptobenzothiazole (Captax), 1.5 parts of tetramethylthiuram i monosulfide (Monex), 1.5 parts of sulfur, and 20 parts of turpentine oligomers Or a comparative plasticizer. The oligomers used were obtained by polymerizing turpentine Plasticity Mooney (Uneured Cure Stock) Index at 280 F. 15 Min.

: Each stock was remilled to provide fresh surfaces, formed into a sheet, placed on a fiat surface, and cooled to room temips is recorded The properties of the elastomer compositions are given Table II.

Ex. No. Plasticizer was determined by the following procedure perature. Strips 1" x 4" were die-cut from the sheets and placed face to face in three pairs. The paired strips were placed between steel plates and loaded with a 24-pound weight for 3 minutes. Each pair of strips was then separated using a modified Scott L-6 Tester. The average pull required to separate the three pairs of str Table II.

8 From the data in Tables I, II, and Ill, it will be seen that the terpene oligomers, whether used alone or in combination with other processing agents, are effective as combined softener-plasticizers and tackifiers for ethylene-u- 5 olefin elastomer compositions. The oligomers are com- Sfiigfigg patible with both oil-extended and non-extended polymers,

and they soften the polymers and render them tacky without adversely affecting their cure rate or their physical Q g g Q .3 g properties.

10 The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.

What is claimed is: 1. A composition comprising an elastomeric terpolymer containing approximately 25% to 75% by weight of ethylene monomer units, to 75 by weight of propylene monomer units, and 0.5% to 5% by weight of units of monomers selected from the group consisting of 1,3-butadiene, isoprene, 1,3-pentadiene, 1,4-hexadiene, di-

ofofcsfofofoi cyclopentadiene, S-methylene-Z-norbornene, 5-(2'-ethy1- 25 2-butenyl)-2-norbornene, and 2-ethyl-2,5-norbornadiene and approximately 1 percent to 35 percent by weight, based on the weight of said terpolymer, of oligomers of cyclic monoterpene hydrocarbons, said oligomers having the formula (C H where n represents an integer in gggggg the range of 2 to 4, and having boiling points in the range of 170 to 240 C. at 10 mm. pressure.

2. A composition as set forth in claim 1 which contains 6 10 percent to 20 percent by weight, based on the weight of said terpolymer, of said terpene oligomers.

"' 3. A composition as set forth in claim 1 which contains 10 percent to 20 percent by weight, based on the egggag weight of said terpolymer, of dipentene oligomers. wwmciow 4. A composition as set forth in claim 1 which contains 10 percent to 20 percent by weight, based on the 4.0 weight of said terpolymers, of pinene oligomers.

5. A composition comprising an elastomeric terpolymer .4 containing approximately 25% to 75 by Weight of ethylene units, 25 to 75 by weight of propylene units, and

0.5% to 5% by weight of units of a monomer selected from the group consisting of 1,3-butadiene, isoprene, 1,3-

pentadiene, 1,4-hexadiene, dicyclopentadiene, S-methylene-2-norbornene, 5-(2'-ethyl-2-butenyl) 2-norbornene, and 2-ethyl-2,S-norbornadiene, and as plasticizer-tackifier gggg (a) 10 percent to 20 percent by Weight, based on the weight of said terpolymer of oligomers of cyclic monoterpene hydrocarbons, said oligomers having the formula (C H wherein n represents an integer in the range of 2 to 4 and having boiling points in the range of 170 C. to 240 C. at 10 mm. pressure, and (b) 20 percent to 50 percent, based on the weight of said terpolymer, of a petroleum oil selected from the group consisting of naphthenic, paraffinic, and aromatic oils.

6. The composition of claim 5 wherein the oligomers are dipentene oligomers. 7. The composition of claim 5 wherein the oligomers are pinene oligomers.

8. The composition of claim 5 wherein the petroleum oil is a naphthenic oil.

9. The process of plasticizing and tackifying an elas- 5 tomeric terpolymer containing approximately 25% to 75 by weight of ethylene units, 25 to 75% by weight of propylene units, and 0.5 to 5% by weight of units of a monomer selected from the group consisting of 1,3- butadiene, isoprene, 1,3-pentadiene, 1,4-hexadiene, dicyclopentadiene, S-methylene-Z-norbornene, 5-(2'-ethyl-2- butenyl) 2 norbornene, and 2-ethyl-2,5-norbornadiene which comprises incorporating in said terpolymer approxi mately 1% to 35%, based on the weight of the terpolymer, of oligomers of cyclic monoterpene hydrocarbons, said 7 oligomers having the formula (C H Q wherein n rep- 3A Turpentine dimers containing no higher polyn1ers 3B. Turpentine dimers containing 3.5% higher polymers 3C. Turpentine dimers containing 11% higher polymers. 3D Paraffin oil (Mobilsol 55) 3E Naphthenicoil (Necton 60)...." 3F None 9 resents an integer in the range of 2 to 4, and having boiling points in the range of 170 C. to 240 C. at 10 mm. pressure.

10. The process of claim 9 wherein 10 percent to 20 percent, based on the weight of the terpolymer, of dipentene oligomers is incorporated into the terpolymer.

11. The process of claim 9 wherein 10 percent to 20 percent, based on the weight of said terpolymer, of pinene oligomers is incorporated into the terpolymer.

12. The process of claim 9 wherein (a) 10 percent to 20 percent, based on the Weight of said terpolymer, of oligomers of cyclic mono terpene hydrocarbons, said oligomers having the formula (C H wherein n; represents an integer in the range of 2 to 4 and (b) 20 percent to 50 percent, based on the weight of said terpolymer, of a petroleum oil selected from the group consisting of ntphthenic, paraifinic, and aromatic oils is incorporated into the terpolymer.

13. The process of claim 12 wherein the oligomers are dipentene oligomers.

14. The process of claim 12 wherein the oligomers are pinene oligomers.

15. The process of claim 12 wherein the petroleum oil is a naphthenic oil.

References Cited UNlTED STATES PATENTS 3,175,986 3/1965 Apikos 260-27 2,741,651 4/1956 Been 26027 2,409,276 10/ 1946 Harvey 260-29.8 3,025,167 3/1962 Butler 26028.5 3,171,824 3/1965 Young.

FOREIGN PATENTS 676,351 12/1963 Canada.

OTHER REFERENCES Alliger, Vulcanization of Elastomers, 1964, Reinhold Pub. Co., pages 316 and 317.

Mzourek, Plaste and Kautsche, vol. 7, 1960, pages 396- 398.

Condensed Chemical Dictionary, 6th edition, pages 894, 404, 1961.

Du Pont, Nordel, April 1964; pages 25 and 26.

MORRIS LIEBMAN, Primary Examiner.

S. L. FOX, Assistant Examiner.

US. Cl. X.R. 26033.6 

